Dosimetric quality and evolution of edema after low-dose-rate brachytherapy for small prostates: Implications for the use of newer isotopes

作者：Kovtun Konstantin A; Wolf**erger Luciant; Niedermayr Thomas; Sugar Emily N; Graham Powell L; Murciano Goroff Yonina; Beard Clair; D'Amico Anthony V; Martin Neil E; Orio Peter F; Nguyen Paul L^*

来源：Brachytherapy, 2014, 13(2): 152-156.

DOI：10.1016/j.brachy.2013.05.006

• Prostate brachytherapy
• Low dose rate
• Small prostate
• (1251) seeds

PURPOSE: To characterize prostate swelling and dosimetry in patients with small ptostate volumes (PVs) undergoing brachytherapy.
METHODS AND MATERIALS: We studied 25 patients with PV < 25 cc (range, 15.1-24.8) and 65 patients with PV >= 25 cc (range, 25.0-66.2) based on three-dimensional ultrasound contours who underwent brachytherapy monotherapy with intraoperative planning. Postoperative Days 1 and 30 dosimetry was done by CT-MRI fusion.
RESULTS: Small PVs had greater Day 1 swelling than large PVs (32.5% increase in volume vs. but by Day 30, swelling was minimal and not significantly different (p = 0.44). Small PVs had greater seed and needle densities at implant (p < 0.001). Rectal and urethral doses were nearly identical by Day 30 (small PV rectum receiving 100% of the prescription dose [145 Gy] [V-100] = 0.32 cc; large PV rectum V-100 = 0.33 cc, p = 0.99; small PV urethra receiving 150% of the prescription dose [145 Gy] [V-150] = 0.20, large PV urethra V-150 = 0.20, p = 0.91). Swelling at Day 1 created some cool implants (rate dose that covers 90% of the prostate volume [D-90 < 140 Gy = 12.0% and 9.4% for the small and large PV groups, respectively, p = 0.71), but Day 30 planning target volume coverage was excellent (rate D90 < 140 Gy = 0% for both groups).
CONCLUSIONS: Although smaller prostates have greater Day 1 swelling, good Day 30 dosimetry can be achieved, making them excellent candidates for I-125 seeds (half-life [M] = 60 days). Smaller prostates may be suboptimal for shorter t(1/2) sources such as Cs-131 (t(1/2) = 9.7 days), in which the majority of the dose may be delivered to an edematous gland, unless the planning is adjusted to anticipate the edema.

• 出版日期2014-4